How do I make this script run silently?

Hi,

My company uses a lot of automated faxing and our sent items folder on the server becomes very large rather quickly. I am currently using this script to clear out all items older than 30 days. The script works well. The only problem is that every time the script is run it requires my interaction. I would like to set this to run automatically as a scheduled task so that I do not have to manually run and click yes for every item being deleted. Or is there a better script to use for this?